1. Field of the Invention
A method for controlling a biaxial wheel test machine to provide accurate wheel camber, or tilt, angle information to data relating to potentially damaging forces applied to input a wheel during a test cycle.
2. Background Art
Laboratory testing of a wheel in a biaxial test machine may require that axial, or lateral, and radial wheel test load data be measured at a test track and translated for programing the biaxial test machine. This is performed by running a weighted prototype wheel through durability procedures while a wheel force transducer mounted on the wheel extracted spindle load data that was uploaded to a central server for analysis by engineering personnel. Wheel durability engineering personnel process data in time/history format into joint probability distributions used in block cycle test profiles for the biaxial test machine.
The data is based on spindle center loading but the test machine requires that inputs be translated into a tire sidewall input. The translation is based on an expectation of tire life and a necessity to run the tire against a drum to generate axial forces instead of using a tire patch (a footprint of a tire in contact with the ground), that increases tire temperature and wear.
Strain gauges may be attached to high-stress areas of a wheel that is mounted on a Flat-Trac® machine. A Flat-Trac® machine includes a moving belt against which a tire is pressed. The wheel may be loaded to reflect the axial and radial wheel test load data. The machine provides spindle load control and records outputs from the strain gauges.
The wheel is mounted on the biaxial wheel test machine and is loaded to reflect the axial and radial wheel test load data recorded by the Flat-Trac® machine. The wheel may be tilted to various camber, or tilt, angles while each axial and radial load pair is applied. Actual strain measurements are correlated with those recorded by the Flat-Trac® machine with the camber angles being compared with the loads to provide a simulation of track loads.
A process described in U.S. Pat. No. 6,813,938 to Schwendemann, issued on Nov. 9, 2004, proposes a simplification of the previously described correlation process. The Schwendemann patent is intended to enable the calculation of camber angles without having to apply strain gauges to a wheel and without having to use a Flat-Trac® machine. The Schwendemann process includes locating an additional load cell in a biaxial test machine to track camber load, and further includes using geometry to calculate a camber angle that matches a requested load pair.
There is a need for greater precision in determining the degree of wheel camber angle when measuring potential damage to a wheel.